The data for the top 10 countries are being pulled from the Census Bureau's International Database. Here's the US data: http://www.census.gov/population/interna

The data for the top 10 countries are being pulled from the Census Bureau's International Database. Here's the US data: http://www.census.gov/population/international/data/idb/region.php?N=%20Results%20&T=13&A=separate&RT=0&Y=2014&R=-1&C=US http://www.census.gov/population/international/data/idb/regi... There, you can see 2014's mid-year population is identical to the top 10 chart. So 318,892,103 is the estimated mid-year population for 2014 (July 1), whereas 317,760,552 is the estimated population as of today (March 27).